The embodiments herein relate to dual purpose viscosifier-scale inhibitors for use in subterranean formation operations.
Subterranean wells (e.g., hydrocarbon producing wells, water producing wells, and the like) are often stimulated by hydraulic fracturing treatments. In hydraulic fracturing treatments, a treatment fluid is pumped into a portion of a subterranean formation at a rate and pressure such that the subterranean formation breaks down and one or more fractures are formed. Typically, particulate solids, such as graded sand, are suspended in a portion of the treatment fluid and then deposited into the fractures. These particulate solids, or “proppant particulates,” serve to prop the fracture open (e.g., keep the fracture from fully closing) after the hydraulic pressure is removed. By keeping the fracture from fully closing, the proppant particulates aid in forming conductive paths through which produced fluids, such as hydrocarbons, may flow.
The degree of success of a fracturing operation depends, at least in part, upon fracture porosity and conductivity once the fracturing operation is complete and production has begun. Thus, the proppant particulates should be substantially evenly distributed throughout the treatment fluid such that a sufficient number of the proppant particulates are placed within a fracture to prop the fracture open. For this reason, viscosified treatment fluids are typically used to place proppant particulates into a fracture in a subterranean formation because the viscous nature of the treatment fluid is capable of maintaining the proppant particulates in suspension and reduce their tendency to settle out of the treatment fluid prior to reaching said fracture or other desired placement zone. The treatment fluids may be viscosified using gelling agents such as natural and synthetic polysaccharides (e.g., guar gums, cellulose derivatives, and the like), and/or combinations thereof. In some cases, the gelling agents may be crosslinked to further viscosify the treatment fluids.
In addition to viscosifing the treatment fluids, the gelling agents may additionally provide fluid loss control. As used herein, the term “fluid loss control” refers to reducing or preventing the volume of filtrate that passes through a filter medium. Specifically, the gelling agents may prevent the loss of the aqueous phase or other liquid phase of a treatment fluid from seeping into or otherwise becoming lost in permeable portions of a subterranean formation (e.g., a fracture or a proppant pack). Failure to control fluid loss may result in a reduction in the efficiency of a treatment fluid, such that the fluid is unable or less effective at propagating fractures or suspending proppant particulates.
In some cases, prior to, during, or after the production of a fractured subterranean formation, a scale inhibitor is placed into the formation to inhibit the formation of scale deposits in the production conduit. As used herein, the term “scale” refers to a mineral deposit or coating formed on the surface of metal, rock, or other material and “scale inhibitor” refers to a chemical agent or treatment used to control such deposition or coating. Scale inhibitor treatment fluids may traditionally be continuously injected into a wellbore through an injection port, for example, during completion operations. In some cases, a scale inhibitor is included with the treatment fluids comprising gelling agents used to fracture a subterranean formation, such that the scale inhibitor absorbs into the matrix and dissolves therein to prevent or reduce scale deposition. The scale inhibitor does not itself contribute to the productivity resulting from fracture stimulation and may increase the expense of a fracturing operation. Likewise, the gelling agent does not itself contribute to scale inhibition.